Thermal breakthrough calculations to optimize design of a multiple-stage Enhanced Geothermal System
Thermal breakthrough calculations to optimize design of a multiple-stage Enhanced Geothermal System
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DOI：
10.1016/j.geothermics.2016.06.015
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发表时间：
2016-11-01
期刊：
影响因子：
3.9
通讯作者：
McClure, Mark W.
中科院分区：
文献类型：
--
作者：
Li, Tianyu;Shiozawa, Sogo;McClure, Mark W.
我们对具有水平井和多个压裂阶段的增强型地热系统 (EGS) 的设计进行了优化和敏感性分析。灵敏度分析包括热突破和系统可达到的最大流量的计算。该分析使用理想化的储层几何形状，旨在研究参数之间的关系并深入了解如何优化 EGS，而不是提供精确的性能预测。传统上，EGS 井几乎是垂直的，并且采用单阶段裸眼完井进行增产。本研究研究了具有两个平行水平井的设计。第一口井用套管钻完，然后用额定高温的套管封隔器分阶段进行增产。第二口井穿过第一口井周围形成的增产区域并完成裸眼井。对于井距、横向长度、地层渗透率和级数的不同组合，我们计算使收入现值最大化的最佳流量。计算表明，多级刺激极大地提高了经济绩效，延迟了热突破，并允许更高的流量通过系统循环。在低井距和低级数的情况下，最好以比最大可能速率更慢的速度循环流体，以延迟热突破。井距越大，级数越多，热突破相对延迟，并且最好以最大可能的流速循环。总的来说，最好使用最小的井距，通过以最大可能的速率循环来最大化现值。当以最大可能速率循环时，当前值对储层透射率敏感。当最佳循环速度小于最大可能速率时，当前值不受储层透射率的影响。将横向长度增加到 1000 m 以上仅对横向间距相对较小和级数较多的设计有利。 (C) 2016 作者。由爱思唯尔有限公司出版
We perform an optimization and sensitivity analysis for design of an Enhanced Geothermal System (EGS) with horizontal wells and multiple fracturing stages. The sensitivity analysis includes calculations of thermal breakthrough and the maximum flow rate that can be achieved through the system. The analysis uses idealized reservoir geometry and is intended to investigate the relationship between parameters and provide insight into how to optimize an EGS, not to provide precise predictions of performance. Conventionally, EGS wells have been nearly vertical and stimulated with openhole completion in a single stage. This study investigates a design with two parallel horizontal wells. The first well is drilled and completed with casing, and then stimulated sequentially in stages with cased hole packers rated to high temperature. The second well is drilled through the stimulated region created around the first well and completed openhole. For different combinations of well spacing, lateral length, formation permeability, and number of stages, we calculate the optimal flow rate that maximizes the present value of revenue. The calculations show that stimulating with multiple stages greatly improves economic performance, delays thermal breakthrough, and allows a higher flow rate to be circulated through the system. At low well spacing and low number of stages, it is optimal to circulate fluid more slowly than the maximum possible rate in order to delay thermal breakthrough. With greater well spacing and with more stages, thermal breakthrough is relatively delayed, and it is optimal to circulate at the maximum possible flow rate. Overall, it is optimal to use the lowest well spacing where present value is maximized by circulating at the maximum possible rate. When it is optimal to circulate at the maximum possible rate, present value is sensitive to reservoir transmissivity. When it is optimal to circulate at less than the maximum possible rate, present value is unaffected by reservoir transmissivity. Increasing lateral length beyond 1000 m is only beneficial for designs with relatively low lateral spacing and a large number of stages. (C) 2016 The Author(s). Published by Elsevier Ltd.